1. Field of the Invention
The present invention relates to a device for adjusting valve duration using an external air supply and more particularly, to an improved device for adjusting valve duration using an external air supply, including an operating chamber with a piston, and inner and outer valve spring seats with wax whereby in a vehicle travelling at low speed, when engine oil has a high pressure, the heated air may expand the wax and compress a valve spring for adjusting the valve duration so as to effectively improve output power of the vehicle engine.
2. Description of Related Art
Various types of valve duration adjusting devices are known in the art. Generally, inlet and exhaust valves installed on a vehicle cylinder head function to induce air or mixed air into a vehicle cylinder, exhaust combusted gas, and prevent gas leakage by adhering to a valve seat in compression and explosion strokes.
Also the inlet and exhaust valves of the vehicle have to proceed with their respective functions. That is, while the vehicle piston operates in a circle, the inlet and exhaust valves have to accomplish intake and exhaust functions so as to improve efficiency of the cylinder. The inlet and exhaust valves are operated by a rocker arm which is operated by a cam which is rotated by a crank shaft through a timing belt.
Generally, there are two methods in the adjusting opening time of the inlet and exhaust valves. One of them is a valve timing adjusting method and the other is a valve duration adjusting method. That is, the valve timing adjusting method provides an adjusting method of a phase angle of the cam shaft, and the valve duration adjusting method provides a selective operating method of a pair of low and high rocker arms.
Usually, the vehicle engines are classified as a low output power engine in order to drive on a local road, and a high output power engine in order to drive on the highway. The low output power engine is a single over head cam shaft (SOHC) and the high output power engine is a double overhead cam shaft (DOHC). The SOHC engine is designed such that an amount of mixed air induced into the combustion chamber is at a maximum during opening to closing of the inlet valve in a low rpm, for example, 2,000-3,000 rpm. The DOHC engine is designed such that an amount of mixed air induced into the combustion chamber is at a maximum during opening to closing of the inlet valve in a high rpm, for example, 3,500-4,000 rpm.
However, if a vehicle designed as a low speed engine is driving in a high speed, the vehicle will suffer from a number of problems such as, for example, breaking power balance since all parts conflict mechanically and the intake manifold has resistance due to inertia of the piston and the valve train system, and reducing the intake efficiency since the mixed air induced into the combustion chamber flows backward to the intake manifold or the mixed air leaks to the outside through the exhaust manifold.
At this time, the actual amount of mixed air induced into the combustion chamber decreases when compared with the regular low speed state as shown in FIGS. 1(A) and 1(B). In FIG. 1(A), an amount of mixed air shown in a hashed line area is of an improper concentration, and in FIG. 1(B), an output power of the vehicle engine declines as shown in a solid line thereof.